Method and apparatus for reducing power consumption in a multimode terminal when performing IP communications

ABSTRACT

An apparatus for reducing power consumption in an IP (Internet Protocol) communications device. The apparatus may include a high-power consumption main application processor and a low-power consumption application processor to share processor functions. The high-power consumption application processor may carry out functions related to the user interface of the device, signaling and control path. The low-power consumption application processor may implement IP processing, voice signal processing and video signal processing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/018,163 (now U.S. Pat. No. 8,301,189), filed on Jan. 22, 2008, whichclaims the benefit of U.S. Provisional Application No. 60/886,166, filedon Jan. 23, 2007. The entire disclosures of the above applications areincorporated herein by reference.

FIELD

The present invention relates generally to power management, and moreparticularly to a method of reducing power consumption in a portable IP(Internet Protocol) communications device, e.g., a multimode device suchas a cellular telephone with Internet communication capabilities.

DESCRIPTION OF RELATED ART

Continued advancements in telecommunication technologies and Internettechnologies have made portable devices with IP capabilities, includingcellular telephones with Internet access, very popular. Since talk timeand standby time are important performance attributes of such devices,techniques for extending battery life or otherwise reducing powerconsumption are becoming increasingly important.

FIG. 1 illustrates an exemplary architecture 100 of an existing dualmode cellular/Wi-Fi phone chipset. As shown, the architecture 100 mayhave an application processor (AP) 101, a Wi-Fi chipset 102 and acellular modem 103. The application processor 101, which may be an ARMprocessor, for example, typically may run at frequencies as high as400-600 MHz, and is a high performance and high-power consumptiondevice. The more the processor 101 is on, the more battery power theprocessor 101 will drain. The Wi-Fi chipset 102 may communicate with theapplication processor 101 via an SDIO (Secure Digital Input/Output)interface 104, and the cellular modem 103 may communicate with theapplication processor 101 via a UART (Universal AsynchronousReceiver/Transmitter) interface 105. The architecture 100 may alsoinclude a RAM (Random Access Memory) 106, a DMA (Direct Memory Access)107, and a bus 108 coupling various components in the architecture 100.The whole IP stack may reside in the application processor 101, whichmay control all Wi-Fi operation, including link maintenance and messagebroadcasting. VoIP (Voice over Internet Protocol) is controlled by theapplication processor 101 as well.

One problem with the architecture 100 shown in FIG. 1 is that theapplication processor 101, running at relatively high frequencies, mayhave to be running at full power constantly because of the variousfunctions the application processor 101 performs, thereby resulting inshorter battery life. Even though, for example, processing telephonecommunications through cellular modem 103 does not require constantactivity (for example, in some known implementations, communication ison for a short period of time, such as 20 ms, and then off for acomparable period of time), the application processor 101 may have to beawake during the whole call because of processing of data from Wi-Fichipset 102. Thus, even when no data is being communicated through thecellular modem 103, the Wi-Fi chipset 102 may be involved in handlingand maintaining a status of various network level protocols, e.g., TCP(Transmission Control Protocol), IPv4, IPv6 and UDP (User DatagramProtocol). The architecture 100 of FIG. 1 may have to keep theapplication processor 101 awake to implement such network protocols. Forexample, for the Wi-Fi chipset 102 to operate at peak performance, theapplication processor 101 may have to control the followingoperations: 1) scanning the radio environment for available accesspoints; 2) connecting to access points in a Wi-Fi communications networkcapable of providing the best bandwidth and QoS (Quality of Service); 3)sending “keep alive” packets to the Wi-Fi access points to maintainconnectivity; and 4) responding and digesting broadcast messages fromthe Wi-Fi access points. These operations may require considerableprocessing time of the application processor 101, and consequently maycause significant battery drain.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention are described herein with referenceto the accompanying drawings, similar reference numbers being used toindicate functionally similar elements.

FIG. 1 illustrates an exemplary architecture of an existing chipset fora multimode portable communications device.

FIG. 2 illustrates an architecture of a chipset for a multimode portablecommunications device according to one embodiment of the presentinvention.

FIG. 3 illustrates a state machine for a call processing procedure whichmay be exchanged by application processors 201 and 220 in FIG. 2.

DESCRIPTION

The present invention provides an apparatus and method for reducingpower consumption in a multimode portable communications device, e.g., acellular telephone with Internet capabilities. The apparatus may includea high-power consumption main application processor, such as a processoroperating at a relatively high frequency, and a low-power consumptionapplication processor, such as a processor or processor core operatingat a lower frequency, to share the functions provided by the processor101 in FIG. 1. Specifically, the high-power consumption applicationprocessor may carry out functions related to the device's userinterface, signaling and control path, which may require less processorawake time. At the same time, the low-power consumption applicationprocessor may implement IP processing, voice signal processing, andvideo signal processing, which may require more processor awake time.Consequently, the awake time of the high-power consumption processor maybe reduced, and battery life of the multimode communications device maybe improved.

FIG. 2 illustrates an architecture 200 of a dual mode cellular/Wi-Fiphone chipset according to one embodiment of the present invention. Thearchitecture 200 may include a high-power consumption main applicationprocessor 201, a low-power consumption application processor 220, aWi-Fi chipset 202 (which may comprise one or more chips) communicatingwith the processors via an SDIO interface 204, a cellular modem 203communicating with the processors via a UART interface 205, a RAM 206, aDMA 207, and a bus 208 coupling various components in the architecture200.

The low-power consumption application processor 220 may implementnetwork level protocols which require a processor to be constantlyawake, and may help to reduce demands for the processing time of themain application processor 201. In one embodiment, the low-powerconsumption application processor 220 may run at 150 MHz, a frequencyconsiderably lower than that of the main application processor 201,which as noted earlier may run at frequencies from 400 to 600 MHz. Ingeneral, the particular frequencies are not important; what matters moreis the allocation of duties between faster and slower processors. In amultimode device, some functions, such as IP-related functions demandingconstant processor attention, may be moved to a low frequency processor.The higher processing capability of the application processor 201 can bereserved for more processor-intensive activities that require fasteroperation, but less “on” time. As a result, the architecture 200 may bemuch more power efficient than the architecture 100. In one embodiment,the low-power consumption application processor 220 may be a Low PowerARM Core.

The network level protocols and functions maintained by the low-powerconsumption application processor 220 may include, e.g., TCP/UDP/IP, RTP(Real-time Transport Protocol)/RTCP (RTP Control Protocol), DHCP(Dynamic Host Configuration Protocol), AJB (Adaptive JitterBuffering)/PLC (Packet Loss Concealment), IKE (Internet Key ExchangeProtocol), including but not limited to IKEv2, AEC (Acoustic EchoCancellation), and a DNS (Domain Name System) client. For example, thefunctions carried out by the application processor 101 in FIG. 1 tomaintain the performance of the Wi-Fi chipset 202 may now be performedby the low-power consumption application processor 220. In addition, thelow-power consumption application processor 220 may also implement voicecodecs for VoIP, e.g., G711/G729ab and AMR (Adaptive Multi-Rate).

With the help of the low-power consumption application processor 220 onnetwork level protocols, the main application processor 201 mayconcentrate on, e.g., the user interface of the device, signaling andcontrol path, and may enter into a sleep mode until the applicationprocessor 201 is awakened by user operation or by other components inthe architecture 200. The main application processor 201 may control,for example, VoIP, a WLAN (Wireless Local Area Network) client, an IMS(IP Multimedia Subsystem) client, a SIP (Session Initiation Protocol)stack, and video signal sharing.

In one embodiment, the functions of the application processor 101 inFIG. 1 may be split between the main application processor 201 and thelow-power consumption application processor 220 in FIG. 2. Thehigh-power consumption application processor 201 may perform signalingand control path setup. Once the signaling and control path setup aredone, the main application processor 201 may send a state machine, asdescribed below, to the low-power consumption application processor 220,and then enter a sleep mode until the application processor 201 isawakened by user operation or by other components in the architecture200. The low-power consumption application processor 220 may thenprocess the media flow.

FIG. 3 illustrates a state machine for a call processing procedure whichmay be exchanged by the application processors 201 and 220. As shown,the state machine may include a number of independent states: start 301,register 302, call setup 303, signaling/controlling 304, media packsetup 305, call up & running 306, and call terminate 307. Each state maymaintain a set of data in a certain data structure indicating status ofthe call processing. For example, the state call setup 303 may maintaininformation about a call, including, e.g., information about the callingparty, called party and the type of codec required; the state media packsetup 305 may maintain RTP/RTCP.

In one embodiment, for an incoming call, the main application processor201 may carry out states 301 to 304, and then may transfer the statemachine to the low-power consumption application processor 220. Thestate machine at this point may indicate that states 301-304 have beencompleted, a call has been set up, and the main processor 201 is readyto receive media signals. The low-power consumption applicationprocessor 220 may receive the state machine, and resume the callprocessing procedure from the state 305 to pick up a required codec andset up a media pack, according to information about the call maintainedat the state 303, call setup. The low-power consumption applicationprocessor 220 may continue to state 306, call up and running, toexchange voice and/or video signals between the calling party and calledparty. When a user hangs up, the low-power consumption applicationprocessor 220 may return the state machine to the main applicationprocessor 201, with the state machine indicating that states 305 and 306have been completed. The main application processor 201 may resume thecall processing procedure from state 307, call terminate, and then mayreturn to state 301 to wait for another call. Since states 305-306 maybe controlled by the low-power consumption application processor 220,the demand for processing time of the main application processor 201 isreduced, and so is the power consumption.

In one embodiment, the low-power consumption application processor 220may be always up and running, so the main application processor 201 maysend a state machine to the low-power consumption application processor220 anytime the main application processor 201 completes an action. Themain application processor 220 can enter a sleep mode when the statemachine is sent to the low-power consumption application processor 220.The low-power consumption application processor 220 may wake up the mainapplication processor 201 when it needs to send a state machine to themain application processor 201.

In one embodiment, the low-power consumption application processor 220may run at a 20 ms sleep/wake cycle. Typical voice communications gothrough 20 ms cycles: 20 ms data processing and 20 ms silence. Thelow-power consumption application processor 220 may wake up during thedata processing cycle to receive and process voice packets, and thenenter into the silence cycle. During the silence cycle, the processor220 may stop processing the voice packets but continue to maintainnetwork level protocols. The silence cycle, which is a form ofsleep-awake cycle but is not what would commonly be termed a “deep”sleep, may help to further extend battery life.

In one embodiment, the low-power consumption application processor 220may be coupled to a DSP (Digital Signal Processor) (not shown) for videosignal processing. In this embodiment, video packets would not gothrough the main application processor 201. Instead, the packets may bediverted to the DSP via the low-power consumption application processor220, decoded, and then sent back and displayed on a display of acellular phone or other multimode device. Power consumption may bereduced, since the main application processor 201 is not involved invideo signal processing.

In one embodiment, the low-power consumption application processor 220may have to handle audio signal processing, video signal processing, andthe IP stack. In this embodiment, the application processor 220 may needconsiderable memory to accomplish these functions. Typically, processorssuch as processor 220 will not have substantial memory. For example, inone embodiment, a low-power ARM core may include 512 KB of static RAM(SRAM). However, accessing external memory may increase powerconsumption. Accordingly, in one embodiment, the low-power consumptionapplication processor 220 may use a flash memory 210 to store audioapplications, video applications and/or the IP stack. When processingaudio signals, the low-power consumption application processor 220 maycall up the audio applications stored in the flash memory 210 viaintelligent paging. When the audio signal processing is finished, theaudio applications may be returned to the flash memory 210. Similarly,the application processor 220 may call up video applications and/or theIP stack when processing relevant signals.

In one embodiment, the IP stack may have seven layers: Application layer7, Presentation Layer 6, Session Layer 5, Transport Layer 4, NetworkLayer 3, Data Link Layer 2 and the Physical Layer 1. Instead of placingall layers on the low-power consumption application processor 220, inone embodiment, layer 1 and layer 2 may be moved to the Wi-Fi chipset202, and layer 7 may be moved to the main application processor 201.Consequently, the Wi-Fi chipset 202 may carry out, e.g., linkmaintenance and message broadcasting functions, without requestingprocessing time of the processors 201 and/or 220. In one embodiment, anIP filter (not shown) may be provided at the input of the Wi-Fi chipset202 to divert signals related to layers 3-6 to the low-power consumptionapplication processor 220, and divert signals related to layer 7 to themain application processor 201. The IP filter may be implemented bysoftware or hardware. Consequently, the demand for the processing timeof processors 201 and/or 220 may be reduced, and the power consumptionmay be reduced as well.

In one embodiment, the display of the multimode communications devicemay be divided into two parts: one part for constantly changing signals,e.g., signal strength, battery level and call time; and another part formore persistent display functions that do not change. To improve powerefficiency, the former may be controlled by the low-power consumptionapplication processor 220, and the latter may be controlled by the mainapplication processor 201.

In one embodiment, the main application processor 201 may maintainconnections with a cellular phone network, while the low-powerconsumption application processor 220 may maintain connections with theInternet and process data from both the Wi-Fi chipset 202 and thecellular modem 203. Since the “on” time of the main applicationprocessor 201 may be significantly reduced, the power efficiency of thechipset 200 may be improved.

Although the embodiments are described with reference to a dual modecellular/Wi-Fi phone chipset, the present invention may be used tohandle other functionality as well. One example of such a device is acell phone with an MP3 or other portable music player, with a low-powerconsumption application processor for downloading music from theInternet, and a high-power consumption application processor to controloperations requiring less processor time, but at a higher processorfrequency. Another example is a cellular phone with hardware andsoftware for providing a map service, such as Google Maps™, or a GPSdevice. In this embodiment, the connection with the website or theserver providing the map service or position location is maintained by alow-power consumption application processor, instead of the phone's mainapplication processor operating at a higher frequency.

Several features and aspects of the present invention have beenillustrated and described in detail with reference to particularembodiments by way of example only, and not by way of limitation.Alternative implementations and various modifications to the disclosedembodiments are within the scope and contemplation of the presentdisclosure. Therefore, it is intended that the invention be consideredas limited only by the scope of the appended claims.

What is claimed is:
 1. A communications device, comprising: a firstprocessor configured to i) operate in one of a plurality of differentmodes including i) an awake mode and ii) a sleep mode; and a secondprocessor in communication with the first processor, wherein while thefirst processor is operating in the awake mode, the first processor isconfigured to i) set up a telephone call initiated via a wirelesstelephone interface, and ii) subsequent to setting up the telephonecall, transfer control of the telephone call to the second processor andtransition to the sleep mode, wherein while the first processor isoperating in the sleep mode, the second processor is configured to i)take control of the telephone call from the first processor, and ii)maintain control of the telephone call, and wherein the second processoris further configured to maintain connections with a wireless networkvia an Internet Protocol interface regardless of whether the firstprocessor is operating in the awake mode or the sleep mode.
 2. Thecommunications device of claim 1, wherein: the first processor isconfigured to operate at a first frequency; and the second processor isconfigured to operate at a second frequency that is less than the firstfrequency.
 3. The communications device of claim 1, wherein: the secondprocessor is configured to, after the telephone call is terminated,instruct the first processor to enter the awake mode.
 4. Thecommunications device of claim 1, wherein the Internet Protocolinterface includes a Wi-Fi chipset.
 5. The communications device ofclaim 1, wherein the wireless telephone interface includes a cellularmodem.
 6. The communications device of claim 1, wherein the firstprocessor is configured to, while operating in the awake mode, control auser interface of the communications device.
 7. The communicationsdevice of claim 1, further comprising: a display configured to displayi) a first indication of a first function of the communications device,and ii) a second indication of a second function of the communicationsdevice, wherein the second processor is configured to control thedisplay of the first indication, and the first processor is configuredto control the display of the second indication.
 8. The communicationsdevice of claim 7, wherein the first indication changes more frequentlythan the second indication.
 9. The communications device of claim 7,wherein the first indication corresponds to at least one of a signalstrength of the telephone call, a battery level of the communicationsdevice, and a length of the telephone call.
 10. A method of operating acommunications device having a first processor and a second processor,wherein the first processor is configured to i) operate in one of aplurality of different modes including i) an awake mode and ii) a sleepmode, the method comprising: while the first processor is operating inthe awake mode, setting up a telephone call initiated via a wirelesstelephone interface using the first processor; subsequent to setting upthe telephone call, transferring control of the telephone call to thesecond processor and transitioning the first processor to the sleepmode; while the first processor is operating in the sleep mode, takingcontrol of the telephone call from the first processor using a secondprocessor; maintaining control of the telephone call using the secondprocessor when the first processor is in the sleep mode; and maintainingconnections with a wireless network via an Internet Protocol interfaceusing the second processor regardless of whether the first processor isoperating in the awake mode or the sleep mode.
 11. The method of claim10, further comprising: operating the first processor at a firstfrequency; and operating the second processor at a second frequency thatis less than the first frequency.
 12. The method of claim 10, furthercomprising, using the second processor, after the telephone call isterminated, instructing the first processor to enter the awake mode. 13.The method of claim 10, wherein the Internet Protocol interface includesa Wi-Fi chipset.
 14. The method of claim 10, wherein the wirelesstelephone interface includes a cellular modem.
 15. The method of claim10, further comprising, using the first processor, while operating inthe awake mode, controlling a user interface of the communicationsdevice.
 16. The method of claim 10, further comprising: displaying afirst indication of a first function of the communications device;displaying a second indication of a second function of thecommunications device; controlling the displaying of the firstindication using the second processor; and controlling the displaying ofthe second indication using the first processor.
 17. The method of claim16, wherein the first indication changes more frequently than the secondindication.
 18. The method of claim 16, wherein the first indicationcorresponds to at least one of a signal strength of the telephone call,a battery level of the communications device, and a length of thetelephone call.